In this chapter, we examine how bilingualism affects the minds and brains of users of more than one language. Recent research in this area suggests that the continual cross-linguistic interaction that bilinguals experience at the lexical, syntactic, and phonological levels discussed in Chapters 1 and 3 enhances cognitive abilities related to attentional focus and inhibitory control, referred to as executive function skills. In turn, executive function abilities have important consequences for the development of literacy and academic ability in bilingual children. In addition, we discuss findings regarding the neuroanatomical consequences of bilingualism, and what is known about how these relate to the linguistic and cognitive experiences of bilinguals. While we highlight research conducted on Spanish-speaking bilinguals, we also include important findings from studies investigating bilingual speakers of other languages.

Bilingualism from the perspectives of neuroscience, cognitive psychology, and linguistics

Scientists approach the study of bilingualism in the mind and brain from various disciplines, each of which uses its own methodologies and theoretical frameworks. Neuroscientists examine how multilingualism affects the structure or activation of brain regions by using magnetic resonance imaging to investigate the density of gray matter in monolinguals versus bilinguals, for instance Mechelli, Crinion, Noppeney, O'Doherty, Ashburner, Frackowiak, and Price (2004), or comparing patterns of activation in the brains of monolinguals and bilinguals using neuroimaging techniques such as fMRI, MEG, PET, and EEG. Cognitive psychologists and psycholinguists investigate how bilinguals process language in real time via methods such as eye tracking and reaction-time measures. For example, psycholinguists use reaction-time tasks to measure how quickly bilinguals can name cognates in their two languages compared to words that are non-cognates (Costa, Caramazza, and Sebastian-Galles 2000). Linguists study how bilingualism affects linguistic knowledge via phenomena such as code-switching and language change, using grammaticality judgments, phonemic discrimination tasks, natural speech analyses, and corpus studies (among other methods) to carry out their research.